In thermally assisted magnetic recording, information bits are recorded on a storage layer at elevated temperatures, and the size of the heated area in the storage layer determines the data bit dimension. One way to achieve a tiny confined heating area is to use an optical near-field transducer, such as a plasmonic optical antenna and an aperture, integrated in an optical waveguide having a high refractive index contrast. Light propagating in such an optical waveguide can be focused by an optical focusing element, such as a planar solid immersion mirror. However, it can be challenging to launch light into the optical waveguide of a slider with low-cost, with good alignment tolerance, and with high light delivery efficiency. Embodiments described below provide solutions to these and other problems, and offer other advantages over the prior art.